Spring brake actuator

ABSTRACT

A spring brake actuator is for braking a wheel of a vehicle. The spring brake actuator has an axially elongated housing having a parking brake chamber and a service brake chamber; a main compression spring in the parking brake chamber; a flexible diaphragm in the parking brake chamber; and a pressure plate in the parking brake chamber, the pressure plate located axially between the main compression spring and the flexible diaphragm. The flexible diaphragm has a contoured portion that inhibits radial shifting of the pressure plate with respect to the flexible diaphragm.

FIELD

The present disclosure relates to vehicle braking systems, and inparticular to pneumatically-operated spring brake actuators for engaginga wheel brake.

BACKGROUND

Trucks, trailers and other vehicles often have pneumatically-operatedspring brake actuators, which provide the braking force necessary tostop the vehicle. A brake pedal is positioned on the floor of thevehicle's cab and, upon activation, causes pressurized air from areservoir to enter the spring brake actuator, which in turn causes apush rod to extend out of the spring brake actuator and activate a wheelbrake. The wheel brake typically has brake shoes with a brake liningmaterial that is pressed against a brake drum at the vehicle wheel-endto thereby brake the vehicle. The wheel brake often includes a slackadjustor which turns a cam roller via a camshaft so as to force thebrake shoes to engage the brake drum and brake the vehicle. Releasingthe pressurized air from the air chamber allows a spring within the airchamber to retract the push rod back to its original position.

U.S. Patent Publication No. 2018/0281767 is incorporated herein byreference and discloses a known spring brake actuator. The spring brakeactuator has a push rod assembly with a base located in a service brakechamber and a push rod extending from a service brake chamber. Pneumaticactivation of the spring brake actuator causes the push rod to furtherextend out of the service brake chamber to thereby engage a wheel brakewith a wheel of the vehicle. Pneumatic deactivation of the spring brakeactuator causes the push rod to retract back into the service brakechamber to thereby disengage the wheel brake from the wheel of thevehicle.

The following U.S. Patents further describe the state of the art and arealso incorporated herein by reference in entirety: U.S. Pat. Nos.10,059,322; 9,297,392; 9,050,958; 8,522,666; 6,394,462; 6,314,861;6,405,635; 5,791,232 and 5,285,716.

SUMMARY

This Summary is provided to introduce a selection of concepts that arefurther described herein below in the Detailed Description. This Summaryis not intended to identify key or essential features of the claimedsubject matter, nor is it intended to be used as an aid in limitingscope of the claimed subject matter.

In examples disclosed herein, a spring brake actuator is for braking awheel of a vehicle. The spring brake actuator has an axially-elongatedhousing having a parking brake chamber and a service brake chamber; amain compression spring in the parking brake chamber; a flexiblediaphragm in the parking brake chamber; and a pressure plate locatedaxially between the main compression spring and the flexible diaphragm.According to the present disclosure, the flexible diaphragm has acontoured portion that advantageously inhibits radial shifting of thepressure plate with respect to the flexible diaphragm.

An assembly for a spring brake actuator for braking a wheel of a vehicleis also provided. The assembly includes the flexible diaphragm forlocation in a parking brake chamber of the spring brake actuator, and apressure plate for location between a main compression spring of thespring brake actuator and the flexible diaphragm. The pressure plate hasa hub portion, a radially outer diameter, and flange that radiallyextends from the center column to the radially outer diameter. Theflexible diaphragm includes a contoured portion that abuts and wrapsaround an entirety of the radially outer diameter, at least when themain compression spring is in an extended position, thus inhibitingradial shifting of the pressure plate with respect to the flexiblediaphragm.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of exercise machines are herein disclosed with reference to thefollowing drawing figures. The same numbers are used throughout toreference like features and components.

FIG. 1 is a perspective view of a spring brake actuator according to thepresent disclosure.

FIG. 2 is an exploded view of the spring brake actuator.

FIG. 3 is a perspective view of an assembly for the spring brakeactuator, including a flexible diaphragm and pressure plate.

FIG. 4 is a sectional view of the flexible diaphragm.

FIG. 5 is a sectional view showing the spring brake actuator with itsparking brake chamber in a pressurized condition.

FIG. 6 is a sectional view showing the spring brake actuator with bothof its parking brake chamber and service brake chamber in a pressurizedcondition.

FIG. 7 is a sectional view showing the spring brake actuator with themain compression spring engaged and neither the parking nor the servicebrake chambers in a pressurized condition.

DETAILED DESCRIPTION

FIG. 1 depicts a spring brake actuator 10 for braking a wheel of avehicle. The spring brake actuator 10 has an axially elongated housing12 formed by opposing cup-shaped end portions 14, 16, and anintermediate portion 18 located axially between the cup-shaped endportions 14, 16. The cup-shaped end portions 14, 16 have perimeterflanges 20, 22, respectively, that are engaged in sealing relationshipwith opposing perimeter flanges 24, 26, respectively, on theintermediate portion 18. Ports 28, 30 are located on the intermediateportion 18 and are configured to admit and release compressed air to andfrom the housing 12 during operation of the spring brake actuator, aswill be described further herein below.

Referring to FIGS. 2 and 5-7, the intermediate portion 18 has an innerwall 32 that bifurcates the interior of the housing 12 into a parkingbrake chamber 34 and an opposing service brake chamber 36. A flexiblediaphragm 38 is located in the parking brake chamber 34 and has aradially outer diameter 40 that is clamped and compressed between theperimeter flanges 20, 24 of the cup-shaped end portion 14 andintermediate portion 18. A flexible diaphragm 42 is located in theservice brake chamber 36 and has a radially outer diameter 44 that isclamped and compressed between the perimeter flanges 22, 26 of thecup-shaped end portion 16 and intermediate portion 18. The flexiblediaphragm 38 divides the parking brake chamber 34 into upper and lowercavities 46, 48. The flexible diaphragm 42 divides the service brakechamber 36 into upper and lower cavities 50, 52.

A main compression spring 54 is located in the upper cavity 46 of theparking brake chamber 34 and has a first end compressed against theinner end wall 56 of the cup-shaped end portion 14 and an oppositesecond end compressed against a pressure plate 58, which is locatedaxially between the main compression spring 54 and the flexiblediaphragm 38. The pressure plate 58 has a hub portion 59 and a radialflange 61 that extends from the hub portion 59 to a radially outerdiameter 63. The opposite, second end of the main compression spring 54encircles the hub portion 59 and abuts the radial flange 61.

A push rod assembly 60 has a first end portion 65 abutting the flexiblediaphragm 38 and an opposite, second end portion 67 extending out of theservice brake chamber 36. The second end portion 67 is pivotably coupledto a lever arm 64 of a conventional slack adjuster or cam roller, aportion of which is shown in the drawings. The slack adjuster and/or camroller is configured to translate reciprocal movement of the push rodassembly 60 to a cam roller and wheel brake for the vehicle, as isconventional and thus not further described herein. The type andconfiguration of push rod assembly can vary from that which is shown. Inthe illustrated example, the push rod assembly 60 includes a rod 68 thatis located in the lower cavity 52 of the service brake chamber 36, andextends through a centerhole in the end wall 69 of the cup-shaped endportion 16. Thus, the rod 68 is disposed partially inside and partiallyoutside of the service brake chamber 36. A radial end flange on the rod68 forms a pressure plate 70 that abuts the flexible diaphragm 42 sothat, as will be described further below, as the flexible diaphragm 42flexes back and forth in the chamber, the rod 68 reciprocates furtherout of and back into the lower cavity 52 of the service brake chamber36.

The push rod assembly 60 further includes an extension rod 72 thatextends through centerhole in the inner wall 32 of the intermediateportion 18 of the housing 12, and particular though a boss 76 containingO-ring seals 78 forming an airtight seal along the slideable extensionrod 72. An end plate 80 is coupled to one end of the extension rod 72 bya fastener. The end plate 80 abuts the flexible diaphragm 38 oppositethe pressure plate 58. An end plate 84 is coupled to the opposite end ofthe extension rod 72 by a fastener. The end plate 84 abuts the flexiblediaphragm 42 opposite the pressure plate 70. The pressure plate 58 has acenter cavity 71 in which the end plate 80 nests so as to effectivelymate the end of the extension rod 72 and the pressure plate 58, with theflexible diaphragm 38 sandwiched there between. A return spring 86 islocated in the lower cavity 48 of the parking brake chamber 34 and has afirst end compressed against the end plate 80 and an opposite, secondend compressed against the inner wall 32 of the intermediate portion 18of the housing 12. A return spring 88 is located in the lower cavity 52of the service brake chamber 36 and has a first end compressed againstthe pressure plate 70 and an opposite, second end compressed against theinner end wall 69 of the cup-shaped end portion 16.

FIGS. 5-7 depict the spring brake actuator 10 during various operationalstates. FIG. 5 depicts the spring brake actuator 10 in a state where thewheel brake is released and the vehicle may be driven. Pressurized airis provided via the port 28 to the lower cavity 48 of the parking brakechamber 34. The air pressure pushes the flexible diaphragm 38 upwardlyin the figure, thereby compressing the main compression spring 54 andretracting the extension rod 72 into the lower cavity 48, as shown. Thereturn spring 88 pushes the flexible diaphragm 42 upwardly in thefigure, thereby retracting the rod 68 into the lower cavity 52 of theservice brake chamber 36, as shown at arrow 92.

FIG. 6 depicts the spring brake actuator 10 in a state where the vehicledriver presses down on the vehicle wheel brake pedal, which causespressurized air to be provided via the port 30 to the upper cavity 50 ofthe service brake chamber 36. This causes the flexible diaphragm 42 tomove downwardly in the drawing, compressing the return spring 88. As aresult, the rod 68 is moved downwardly in the figure, as shown by arrow94, outwardly relative to the lower cavity 52 of the service brakechamber 36, thus pivoting the lever arm 64 of the slack adjuster or camroller and causing the wheel brake to be applied.

FIG. 7 depicts the spring brake actuator 10 in a state where the vehicleis off and/or air is otherwise evacuated from the housing 12. When thisoccurs, the main compression spring 54 pushes downwardly in the figureagainst the pressure plate 58, thus pushing the push rod assembly 60downwardly in the figure, as shown at arrow 96, so that the wheel brakesare applied. The spring break actuator 10 can be used in conjunctionwith a variety of conventional brake assemblies, including both brakedrum assemblies and brake disc assemblies.

Thus, pressurizing parking brake chamber 34 compresses the maincompression spring 54 to thereby retract the push rod assembly 60 backinto the service brake chamber 36 and disengage the noted wheel brakefrom the wheel of the vehicle. Depressurizing the parking brake chamber34 allows the main compression spring 54 to move the push rod assembly60 out of the service brake chamber 36 to thereby engage the wheel brakewith the wheel of the vehicle.

Through research and experimentation, the present inventors have soughtto improve upon conventional spring brake actuators of all makes andmodels, and in particular to provide an improved spring brake actuatorthat is less subject to wear over time and thus more robust andlonger-lasting than the prior art. Through research and experimentation,the present inventors have determined that the flexible diaphragmlocated in the parking brake chamber is a component that can wear downover time. This can cause in a reduction in performance, including forexample permitting a displacement (i.e., a radial shifting) of thepressure plate with respect to the diaphragm. Displacement of thepressure plate can make it difficult to efficiently service the brakeactuator, for example by preventing manual access to the pressure platewith a release bolt. Through further research and experimentation, thepresent inventors determined that it would be possible to preventdisplacement of the pressure plate by securing it to the diaphragm withone or more adhesives. However the inventors have also found thatapplication of adhesives is labor-intensive and must be applied underclosely-monitored conditions. The present inventors further realized itwould be possible to prevent this radial shifting by mechanicallyaffixing the pressure plate to the diaphragm with one or more fasteners.However, again, installation of fasteners is labor intensive and thuscostly.

The present disclosure is a result of the present inventors' realizationof the above-described design challenges and their efforts to provide animproved, more robust and long-lasting spring brake actuator that isless costly to manufacture and also less subject to the effects of wearover time, particularly wear of the diaphragm in the parking brakechamber and a resulting displacement of the pressure plate with respectto the diaphragm.

FIGS. 3 and 4 depict the flexible diaphragm 38 according to the presentdisclosure, removed from the spring brake actuator 10 and in a relaxed,natural state. According to the present disclosure, the flexiblediaphragm 38 has a novel contoured portion 100 that advantageouslyinhibits the above-described radial shifting of the pressure plate 58.More specifically, the flexible diaphragm 38 has a radial center portion102 that axially abuts the pressure plate 58 and an intermediate portion104 located radially between the outer diameter 40 of the flexiblediaphragm 38 and the radial center portion 102. The intermediate portion104 has an angular sidewall 106 that radially inwardly funnels from theradially outer diameter 40 to the contoured portion 100. The contouredportion 100 is located along the intermediate portion 104 and defines apocket 108 (see FIG. 4) in which the radially outer diameter 63 of thepressure plate 58 is disposed.

As shown by comparison of FIGS. 5-7, the contoured portion 100 willdeform during movement of the main compression spring 54 into andbetween its compressed position (FIG. 5) and its extended position (FIG.7). As shown by comparison of FIGS. 5 and 7, movement of the maincompression spring from the compressed position to the extended positioncauses the flexible diaphragm 38 to axially invert relative to theradially outer diameter 40 of the flexible diaphragm 38. In certainembodiments, when the main compression spring 54 is fully compressed,the contoured portion 100 becomes deformed such that the pocket 108changes from a concave shape (see FIGS. 4 and 7) in which the outerdiameter 40 is nested, to a convex shape (see FIGS. 5-6) forming aradially outer shoulder of the extended flexible diaphragm 38. However,at least when the main compression spring 54 is fully compressed, thecontoured portion 100 advantageously inhibits radial shifting of thepressure plate 58 with respect to the flexible diaphragm 38. When themain compression spring 54 is extended (FIG. 7), the pocket 108 abutsand wraps around an entirety of the radially outer diameter. That is,the contoured portion 100 abuts the entirety of the radially outerdiameter 40, or radially outer side surface 40, thereby inhibiting theaforementioned radial shifting.

In the present description, certain terms have been used for brevity,clearness and understanding. No unnecessary limitations are to beimplied therefrom beyond the requirement of the prior art because suchterms are used for descriptive purposes only and are intended to bebroadly construed. The different apparatuses described herein may beused alone or in combination with other apparatuses. Variousequivalents, alternatives and modifications are possible within thescope of the appended claims.

What is claimed is:
 1. A spring brake actuator for braking a wheel of avehicle, the spring brake actuator comprising an axially elongatedhousing having a parking brake chamber and a service brake chamber, amain compression spring in the parking brake chamber, a flexiblediaphragm in the parking brake chamber, and a pressure plate locatedbetween the main compression spring and the flexible diaphragm, whereinthe flexible diaphragm comprises a contoured portion that inhibitsradial shifting of the pressure plate with respect to the flexiblediaphragm; wherein the main compression spring is axially movable intoand between a compressed position and an extended position, wherein thepressure plate has a hub portion and a radial flange that is planar andradially extends from the hub portion to a planar radially outermostdiameter, and wherein the contoured portion abuts the planar radiallyoutermost diameter of the pressure plate, at least when the maincompression spring is in the extended position, thereby inhibiting theradial shifting of the pressure plate; wherein the flexible diaphragmcomprises a radially outermost diameter that is sealed to perimeter ofthe parking brake chamber, and wherein movement of the main compressionspring from the compressed position to the extended position causes theflexible diaphragm to invert relative to the radially outermost diameterof the flexible diaphragm; wherein the flexible diaphragm comprises aradial center portion that axially abuts the radial flange of thepressure plate and an intermediate portion located radially between theradially outermost diameter of the flexible diaphragm and the radialcenter portion, and wherein the contoured portion is located along theintermediate portion; wherein the intermediate portion comprises aplanar angular sidewall that radially inwardly funnels from the radiallyoutermost diameter of the flexible diaphragm to the contoured portion;and wherein the contoured portion has a uniform thickness and defines apocket in which the planar radially outermost diameter of the pressureplate is disposed, at least when the main compression spring is theextended position, and wherein the contoured portion wraps around anentirety of the planar radially outermost diameter of the pressure plateat least when the main compression spring is in the extended positionand thus inhibits the radial shifting of the pressure plate at leastwhen the main compression spring is in the extended position.
 2. Thespring brake actuator according to claim 1, wherein the pressure plateis nested within the contoured portion at least when the maincompression spring is in the extended position.
 3. The spring brakeactuator according to claim 1, wherein the flexible diaphragm has arelaxed state upon removal from the housing, and wherein the contouredportion defines the pocket when the flexible diaphragm is in the relaxedstate.
 4. The spring brake actuator according to claim 1, furthercomprising a push rod assembly having a first end portion abutting theflexible diaphragm and an opposite, second end portion extending out ofthe service brake chamber.
 5. The spring brake actuator according toclaim 1, wherein the main compression spring encircles the hub portionand abuts the flange.
 6. The spring brake actuator according to claim 5,wherein the pressure plate comprises a recessed cavity that mates withthe first end portion of the push rod assembly and a center portion ofthe flexible diaphragm.
 7. The spring brake actuator according to claim6, wherein the first end portion of the push rod assembly comprises anend plate disposed in the recessed cavity, such that the flexiblediaphragm is sandwiched between the end plate and the recessed cavity ofthe pressure plate.
 8. The spring brake actuator according to claim 4,wherein pressurizing the parking brake chamber compresses the maincompression spring to thereby retract the push rod assembly back intothe service brake chamber and disengage the wheel brake from the wheelof the vehicle, and wherein depressurizing the parking brake chamberallows the main compression spring to move the push rod assembly out ofthe service brake chamber to thereby engage the wheel brake with thewheel of the vehicle.